Hitherto, as shown in FIG. 4, conventional copying or printing processes were performed in a copying machine, a multifunction machine, or the like. The control sequence described below was performed: A data receiving unit receives a printing job transmitted from a host computer and the associated printing data. The data receiving unit then requests an image forming unit to form an image. The image forming unit then forms an image in response to the request, and also requests a printing engine to start supplying sheets. The printing engine first supplies a sheet from a sheet storage portion so as to deliver the sheet to a resist roller. Then the printing engine secondarily supplies a sheet so as to transfer and fix the image to the sheet. The sheet is delivered on a tray.
However, in order to accelerate the copying or printing process in the copying machine, multifunction machine, or the like, it is necessary to supply sheets in advance by requesting the start of a primary supply of sheets during the receipt or reading of a print job, or accelerate the transportation speed of the primary supply of sheets. However, the print job capacity varies from a small to a large capacity. Therefore, a special device is necessary as to when the primary supply of sheets should be started to accelerate the copying or printing process.
For example, there is the following given technology: simultaneously with the receipt of a print job from the host computer by a printing job receiving unit, the printing engine (which secondarily supplies a sheet supplied primarily from the sheet storage portion, transfers, and fixes a printing image to the sheet) is requested to start supplying a sheet primarily. The image forming unit forms a printing image from the print job received by the printing job receiving unit and outputs the sheet with the printing image formed thereon to the printing engine. Also simultaneously, the secondary supply of sheets starts whereby a printing time in a printer function performing the print job received from the host computer is shortened.
In the above technology, the start of the analysis of image data in the received print job and the start of the primary sheet supply are performed simultaneously. In this case, a request for the secondary sheet supply is made after the completion of image drawing processing of the image data. Therefore, for example, in the case of the print job in which coded image data described in a page description language (PDL) is decoded and the image data is formed, an image processing time becomes uncertain. The image processing time is the time in which the coded image data is decoded to form image data, and each image data is developed into image data on a page basis. Furthermore in this case, the image processing time takes a long time (for example, one or more hours), which makes it necessary to keep the sheet primarily supplied on a transportation path without supplying it secondarily.